Cryptography / Use of Predictable Algorithm in Random Number Generator

Web and API


Use of Predictable Algorithm in Random Number Generator (CWE-338) is a vulnerability in cryptography that occurs when a predictable algorithm is used to generate random numbers. This can lead to the predictability of the random numbers, allowing an attacker to access sensitive information or bypass authentication measures. According to the OWASP Testing Guide, this vulnerability is primarily found in web and API applications that use random numbers as part of their authentication process.


This vulnerability can lead to serious security issues as an attacker can use the predictable random number to access sensitive data or bypass authentication measures. It can also lead to denial of service attacks or the manipulation of application data. The risk of this vulnerability is high and can lead to serious security breaches.


The best way to address this vulnerability is to use an algorithm that is cryptographically strong when generating random numbers. This algorithm should be designed to provide unpredictable numbers that are difficult to guess. Additionally, the algorithm should be tested regularly to ensure that it is still secure and producing unpredictable numbers.


The following example shows a vulnerable code block with the use of a predictable algorithm in the random number generator.

// Vulnerable code snippet

int getRandomNumber() 
	// Use a predictable algorithm
	int randomNumber = 0; 
	for (int i = 0; i < 10; i++) 
		randomNumber += i; 
	return randomNumber; 

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